1. Field of the Invention
The present invention relates to a composition usable for preventing or treating Escherichia coli type K99 infections comprising a bacteriophage, isolated from nature and capable of infecting Escherichia coli type K99 so as to kill the same, as an active ingredient, and a method for preventing and treating Escherichia coli type K99 infections by using the said composition. More precisely, the present invention relates to a bacteriophage isolated from nature which is characterized by having the genome represented by SEQ. ID. NO: 1 and is capable of killing Escherichia coli type K99 specifically, a composition usable for preventing and treating Escherichia coli type K99 infections comprising the said bacteriophage as an active ingredient, and a method for preventing and treating Escherichia coli type K99 infections by using the said composition.
2. Description of the Related Art
Eshcerichia coli (E. coli) is largely divided into two kinds, one of them is non-pathogenic E. coli which is favorably and beneficially functioning to promote digestion with keeping balance normally with other enterobacteria in animal intestines and the other is pathogenic E. coli which has pilus that helps the adherence of the E. coli to intestine wall to be proliferated and produces enterotoxin causing diarrhea by irritating intestine wall.
Diarrhea caused by such pathogenic E. coli is common in almost every livestock farm in Korea. Diarrhea can be caused by single infection with pathogenic E. coli. However, when the livestock is mixed-infected with bovine rotavirus, coronavirus, and coccidium protozoa, etc, intestinal mucosa is so much damaged as to cause acute diarrhea and to make the symptoms worse.
Diarrhea caused by E. coli is reported world widely, and the incidence rate differs from hygienic control level of the livestock farm. Diarrhea caused by E. coli is also frequently reported in Korea as well, and is known as the most representative bacterial diarrhea. The representative causative strains for diarrhea caused by E. coli are F4 (K88), F5 (K99), F6 (987P), and F41. Even though they are different kinds of causative organisms, they are alike to cause diarrhea in almost every kinds of livestock. E. coli type K99 is known as the enterotoxigenic E. coli (ETEC) causing diarrhea in piglings or calves. The clustering of ETEC in the small intestine of the animals is regulated by the direct adhesion of bacteria to the intestinal epithelial cells. The clustering of ETEC intervenes peristalsis, mucus secretion and movement of villi in a host to cause diarrhea.
Damage by E. coli type K99 infections in livestock industry is huge. Therefore, it is urgent request to develop a method for the prevention and effective treatment of the infections. A variety of anti-bacterial agents have been used to prevent or treat E. coli type K99 infections. However, it is also urgent request to develop an alternative of the conventional anti-bacterial agents, considering the increase of antibiotic resistant bacteria.
The utilization of bacteriophage is now highly drawing our attention as an effective way of treating bacterial disease. In particular, our interests in bacteriophage grow with the preference of nature-friendly method. Bacteriophage is an extremely small microorganism infecting bacteria, which is generally called phage in short. Bacteriophage is proliferating in the inside of bacteria cells after infection. Upon completion of the proliferation, offspring bacteriophages are coming out of the host cells with destroying the host bacteria. The infection of bacteriophage in bacteria is very unique and specific, so only specific bacteria can be infected with a specific bacteriophage. That is, there is a limitation in bacteria that can be infected with bacteriophage. Thus, bacteriophage can only kill specific target bacteria without affecting any other bacteria.
Bacteriophage was first found in 1915 when English bacteriologist Twort was studying on the phenomenon that micrococcus colony was being melted clearly by some reasons. And also, French bacteriologist d'Herelle noticed that Shigella disentriae was melted by something in filtrate of dysentery patient's feces and afterwards he separated bacteriophage independently by the following study and named it bacteriophage which meant ‘eating bacteria’. Since then, bacteriophages corresponding to different pathogenic bacteria including Shigella, Salmonella and Vibrio cholorae have been continuously reported.
Owing to its capability of killing bacteria, bacteriophage has been in the center of our interest to fight with bacterial infection and studies followed thereon. However, since Flemming found out penicillin, antibiotics have been supplied and the study on bacteriophage has been limited in some east European countries and old Soviet Union. It was not until 2000 that the conventional antibiotics demonstrated their problems in use because of increasing antibiotic-resistant bacteria. So, once again, bacteriophage draws out attention as an alternative anti-bacterial agent that can take the place of the conventional antibiotics.
According to the recent tightening of regulation regarding the use of anti-bacterial agents by the government, interest in bacteriophage increases.
The present inventors have tried to develop a composition usable for preventing or treating E. coli type K99 infections by using a bacteriophage isolated from nature and capable of killing E. coli type K99 selectively and tried further to establish a method to prevent or treat E. coli type K99 infections by using the said composition. As a result, the present inventors succeeded in isolation of a proper bacteriophage from nature and obtainment of a sequence of the genome distinguishing the bacteriophage from others, leading to the completion of the present invention by confirming that the composition developed by the inventors could be effectively used for the prevention and treatment of E. coli type K99 infections.